Immunolocalization of selected cytokines and proteases in canine articular cartilage after transarticular loading.

Cytokines and proteases are thought to play a role in the destruction of cartilage and the development of osteoarthritis. The purpose of this study was to document chronological involvement of interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), stromelysin (MMP-3), fibronectin, and alteration in the chondroitin sulphate sulfation pattern. Canine patellae underwent a closed-joint impact to induce the development of osteoarthritis. The animals were killed at 2, 12, 24, and 52 weeks. The patellar damage included cracks in the superficial zone of cartilage and the zone of the calcified cartilage-bone interface, vertical step-off fractures in the zone of calcified cartilage, and loss of proteoglycan around the cracks in the deep and superficial zones of cartilage. With avidin-biotin immunohistochemistry, these specimens were stained with antibodies to IL-1 beta, TNF-alpha, MMP-3, fibronectin, and altered proteoglycan sulfate with the monoclonal antibody 3-B-3. Three of the four specimens obtained at 2 weeks demonstrated a strong cellular and weak matrix staining pattern for IL-1 beta, TNF-alpha, MMP-3, and fibronectin around the cracks in the superficial and transitional zones of cartilage. No consistent staining pattern was noted in the cracks in the deep zone. None of the specimens obtained at 12, 24, or 52 weeks stained for these antibodies. No staining for the abnormal sulfation with the 3-B-3 antibody was evident in any specimen. The specimens obtained at 52 weeks showed healing of the step-off fractures and a filling-in of the proteoglycan loss. This model probably reflects the short-term cartilaginous changes in the patella after trauma; thus, only transient elevations in the cytokines and proteases were evident.